Sens. Marco Rubio and Ted Cruz have turned a position that is near universally agreed upon within both the Democratic and Republican parties—that Syrian President Bashar al-Assad needs to go—into a roiling presidential primary debate.

Cruz, in a much-cited interview with Bloomberg Politics earlier this week, voiced his support for keeping Assad in power as the least-bad option to restoring order to the broken country. “If the Obama administration and the Washington neo-cons succeed in toppling Assad,” Cruz said, “Syria will be handed over to radical Islamic terrorists. ISIS will rule Syria.” He cited the U.S.-supported overthrows of strongmen like Hosni Mubarak in Egypt and Muammar Qaddafi in Libya as recent examples of misguided joint efforts between liberal interventionists (hello, Hillary Clinton) and neoconservatives (hello, Marco Rubio) that ended poorly.

Cruz’s position clashes with a main theme of Thursday’s Republican Jewish Coalition candidates’ forum in Washington D.C., at which all 14 GOP presidential candidates are speaking: that Iran, and governments that align themselves with Iran, are the root of all evil in the region, and all U.S. policy in the region should be oriented around debilitating Iran. That means popping off Iran’s man in Damascus. But the uncertainty about who would take over if Assad is toppled has produced a major debate within Israel itself, and it’s one that now has migrated to the Republican campaign.

Rubio, in a question-and-answer session following his speech to the hawkish pro-Israel crowd, was prepared to argue his side. “As long as Bashar al-Assad is in power, you’re going to have in power two things,” he said. “No. 1, you’re going to have an Iranian puppet, who serves not just as a conduit to Iranian influence in the region, but someone who has actively facilitated anti-Israeli, anti-American terrorism in that region.” Keeping Assad also leaves in power an “irritant,” he added. “As long as Assad is in power you’re going to have in place someone that creates the conditions for the next ISIS to pop up, for the next ISIS to emerge.”

“This simplistic notion,” he concluded, “that ‘leave Assad there because he’s a brutal killer, but he’s not as bad as what’s going to follow him,’ is a fundamental and simplistic and dangerous misunderstanding of the reality of the region.”

(Sen. Lindsey Graham, speaking immediately before Rubio, stuck it more directly: “Ted Cruz says he’d keep Assad in power. I sure as hell will not. I am not going to give Damascus to the Iranians.”)

Each has a compelling case for the hawks concerned most of all about Israel’s security. Which would you rather have next door: an Iranian proxy, or a state that’s likely to stay overrun by terrorists for the indefinite future? The party’s hawkish foreign policy establishment will side with Rubio, who’s promising everything, while others who fear getting bogged down in an extended overseas nation-building effort may find Cruz more preferable. Which means that Cruz’s attacks on Rubio, and Rubio’s counter, have opened a surprising new front of foreign policy debate this week. And the bickering candidates have already managed to cleave the two most important Israel hawks of them all: Sheldon and Miriam Adelson.